The present invention relates to a stereoscopic three dimensional image projector, and more specifically, to a feedback circuit for a three dimensional projector.
Three dimensional (3D) movies and pictures have become a popular form of entertainment due to the increased realism of the images. 3D images utilize the human physical trait of binocular vision. Human eyes are spaced about 2 inches (5 centimeters) apart; therefore each eye sees the world from a slightly different perspective. The brain receives both images and has a binocular vision function that correlates the difference between what each eye sees to determine distance. The determination of the distance provides the 3D effect that a person sees.
To create a binocular image on a two dimensional surface (2D), such as a movie or television screen, the user typically wears glasses. The glasses alter the way that the user views the images to create the simulated 3D effect. Typically there are two types of glasses, passive glasses and active glasses. The type of glasses used will depend on the type of image projection system being used.
Passive glasses rely upon an optical effect created by using different lenses for each eye. The projection system emits a sequential series of images where subsequent images are slightly offset. The images are arranged such that the user sees the first image through a first lens of the glasses (e.g. the right eye) and the second image is seen with the other lens (e.g. the left eye). Since the images are projected quickly, the user does not notice the multiple images, but rather sees a three dimensional effect. With active lenses, the glasses wirelessly communicate with the projector to synchronize the operation of the glasses with the images being displayed. With active glasses, the lenses are typically liquid crystal displays (LCDs) that can switch between transmitting light and blocking light. In this way, the glasses may rapidly switch the left and right lenses between clear and opaque. While the glasses are switching, the television is projecting a series of sequential images. When this switching is synchronized between the television and the glasses, the user experiences a three dimensional effect.
In 3D projectors using both active and passive lenses, synchronization of the images is critical to the functionality of the projector. Because the multiple images projected typically have different polarizations, it is imperative that the light source, imaging device, and polarization modulator within the projector remain synchronized. If these devices are not properly synchronized, the images will not be correctly polarized to create the 3D effect.